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Joining ewes in drought

Erica Kennedy, District Veterinarian, Nyngan

The current drought has obviously had a huge impact on lambs weaned this year; therefore many producers are planning to join next year despite the current seasonal forecasts.

It is imperative that producers plan ahead with feed, knowing that the availability of grain during lambing next year may be scarce (due to lack of harvests and demand for seed).

From lessons learnt this year, the amount ewes need to see out lambing and hopefully raise her lamb/lambs is around 1.3-1.5kg/hd/day.

If the drought breaks in Autumn as is the current prediction then producers need to have planned their feed ahead of time so that they can have as many lambs survive through to weaning as possible next year.

If you have merinos, given the current wool price and feed costs, now is the time to consider running ‘ewes as wethers’ if you do not anticipate you will be able to source/afford feed next year.

Joining ewes without planning for lambing next year will only lead to further ewe loss.

Daylength and effect on ovulation:

Decreasing daylength triggers breeding activity, that is, the oestrus cycle. Also, studies with Merino sheep show that higher ovulation rates occur in autumn.

Research has shown that 33 per cent more Merino lambs were weaned per ewe joined in autumn compared with lambs weaned per ewe joined in spring. The summer solstice is on December 21st and day length starts to decrease after that date.

High conception rates are therefore a combination of factors including the date of joining in relation to seasonal feed supply.

  • Early weaning gives ewes the potential to regain body weight but also relies on this date in relation to the break in the season or drying-off of the season.
  • Ewes joined in December in southern NSW rely on high body weight/fat score to give multiple ovulations coming out of spring, as daylength is not yet decreasing. Likely not the case for many this year – these ewes will likely have a poorer conception rate.
  • Ewes joined in February in southern NSW may have a lower static body weight and lower fat score; they benefit from decreasing daylength.
  • Provided an early autumn season break, ewes joined in April benefit from a dynamic increase in both body weight and fat score as well as from positive effects from decreasing daylength.